What three components does an emotional response consist of?
- Behavioural – muscle movements appropriate for the situation
- Autonomic – facilitates behaviours by providing quick mobilisation of energy for vigorous movement
- Hormonal - reinforce autonomic responses
What is the role of the amygdala in fear?
- The amygdala plays a key role in integrating the different components of a fear response
- When threatening stimuli are perceived, neurons in the central nucleus become activated
- This then sends projections out into the hypothalamus, pons and midbrain
What happens with monkeys with damage to the central nucleus?
- After the central nucleus has been destroyed, animals no longer show fear to stimuli that have been paired with aversive events
- They act more tamely when handled by humans, show lower levels of cortisol and are less likely to incur stress related illnesses
What does animal stimulation of the central nucleus show?
- Stimulation of the CN results in the animal demonstrating physiological and behavioural fear responses
- Long term stimulation of the CN results in stress induced illnesses such as gastric ulcers
What is an automatic emotional response?
A few stimuli result in automatic activation of the central nucleus of the amygdala – loud noises, large animals, heights
What is a conditioned emotional response?
- learn that a particular stimulus or situation is dangerous or threatening
- Conditioned emotional response – a classically conditioned response that occurs when a neutral stimulus is followed by an aversive stimulus
- Conditioned emotional responses evolved to increase an animal’s chance of survival in dangerous situations
In which way are conditioned emotional responses likely to be acquired in humans?
- Socially: e.g. a child may become afraid of dogs by observing someone else’s phobia of dogs
- Through instruction: e.g. if you are told a fire alarm will go off in the event of a fire, it is likely that you experience a fear response upon hearing a fire alarm
What is the amygdala is responsible for establishing a conditioned emotional response?
Physical changes responsible for establishing a conditioned emotional response occur in the Lateral nucleus of the amygdala
What is Extinction of conditioned emotional responses?
- Rather than forgetting the associated, the animal learns that the conditioned stimulus is no longer followed by an aversive stimulus
- The conditioned response is inhibited rather than forgotten
What plays a role in inhibiting conditioned emotional responses and how do we know this?
- The ventromedial prefrontal cortex (vmPFC) plays a role in inhibiting these responses
Lesions to vmPFC impair extinction
Stimulation of vmPFC inhibits conditioned emotional responses
Extinction training activated vmPFC neurons
What are aggressive behaviours in animals often related to?
Reproduction and Self defence
What does it mean that neuronal control of aggressive behaviour is hierarchal?
- We perceive the threat through our sensory systems and this relays information to the hypothalamus and the amygdala
- The hypothalamus and amygdala control the activity of the circuits in the brain stem
- The particular movements that an animal makes when attacking or defending itself are controlled by neural circuits in the brain stem
What is a metabolite of serotonin and what do higher levels of it indicate?
5-HIAA is a metabolite of serotonin (5HT). Increased levels of 5-HIAA in cerebrospinal fluid indicates a higher level of serotonergic activity
Researchers measure rates of 5-HIAA in the cerebrospinal fluid of Rhesus monkeys and then tracked them over a four year period, what did they find?
Monkeys with low 5-HIAA demonstrated risk taking behaviour and a large percentage of them were killed by other monkeys over the 4 period of study
What do genetics studies show about the role of serotonin in anger?
- selective breeding programmes have increased levels of serotonin in both rats and silver foxes
- These animals show increased brain levels of serotonin and 5-HIAA
- These animals display greater tameness and are friendlier in response to human contact
What has research with humans shown about serotonin and anger?
- Lower levels of 5-HIAA in the cerebrospinal fluid are associated with aggression and other forms of antisocial behaviour including assault, arson, murder and child beating
- Prozac, a serotonin agonist, reduces irritability and aggressiveness
What is the role of heredity in aggression?
Higher concordance between MX twins than DZ twins at ages 7 and 9 on measures of antisocial behaviour
What is the role of the ventromedial prefrontal cortex in emotion?
- The ventromedial prefrontal cortex plays an important role in emotional regulation and inhibition of emotional responses
- The vmPFC includes medial orbitofrontal cortex and the subgenual anterior cingulate cortex
- Inputs to the vmPFC provide information about what is going on in the environment and what is being planned in the rest of the frontal lobe
- Outputs from the vmPFC affect a variety of behaviours and physiological responses, including emotional responses organised by the amygdala
Who is a good case study into the role of the ventromedial prefrontal cortex?
Phineas Gage
What did the case study with Patient EVR who had surgery to remove a large orbitofrontal meningioma in the frontal lobes show?
- Dissociation between normal performance of psychological tests and abnormal real-life behaviour
- EVR intact cognitive abilities but poor utilisation of those abilities in real life context
What is the role of the vmPFC?
- Evidence suggests that the vmPFC serves as an interface between the brain mechanisms involved in automatic emotion response and those involved in the control of complex behaviours
- Informant ratings of emotional dysfunction and real world difficulties significantly correlated for patients with damage to vmPFC
In which type of decision making is the vmPFC activated?
Moral dilemmas
What does the amygdala and vmPFC do regarding emotions?
- Amygdala plays an important role in generating emotional reactions and the vmPFC in suppressing negative behavioural consequences of emotional reactions
- Decreased prefrontal activity and increased subcortical activity in the brains of convicted murderers (Raine et al. 1998)
- People with antisocial personality disorder have 11% less volume of grey matter in the prefrontal cortex
- Link between brain volume and serotonergic activity
What is the James-Lange theory of emotion?
- Emotion-producing situation elicits a set of physiological responses
- Emotion-producing situation also elicits certain behaviours
- Feedback from the organs and muscles involved in these responses constitutes how we feel
